(515) Superior Sinonasal Preservation: A Comparative Study of Intensity-Modulated Proton Therapy Versus VMAT for Nasopharyngeal Carcinoma

Introduction: Radiation-induced rhinosinusitis (RiRS) is a common sequela in in nasopharyngeal carcinoma (NPC) patients. Although sinus mucosa disease (SMD) is known to peak approximately three months after radiotherapy, its longitudinal relationship with patient-reported symptoms and clinical implications remain unclear. This study compares intensity-modulated proton therapy (IMPT) and volumetric-modulated arc therapy (VMAT) with an emphasis on sinonasal mucosal preservation and clinical symptom outcomes.

Methods: Patients diagnosed with non-metastatic NPC between April 2022 and December 2024 were included. SMD was assessed using Lund–Mackay (LM) scores derived from serial MRI scans. Sinonasal symptom burden was evaluated using the 22-item Sino-Nasal Outcome Test (SNOT-22). Assessments were performed at baseline and every three months following completion of radiotherapy.

Results: A total of 109 patients were included (IMPT: n=67; VMAT: n=42), with a median follow-up of 29 months. Baseline characteristics were comparable between groups. Trends in SNOT-22 scores closely paralleled MRI-based LM scores over time. The IMPT group demonstrated significantly less severe SMD and more rapid mucosal recovery compared with the VMAT group. At one-year post-radiotherapy, a higher proportion of VMAT-treated patients with SMD had persistent clinically significant symptoms with SNOT-22 >30 (32.6% versus19.6%).

Conclusions: IMPT is associated with reduced severity and faster resolution of SMD, accompanied by lower long-term sinonasal symptom burden. Concordance between radiologic findings and patient-reported symptoms supports their use in identifying patients at risk for persistent sinonasal morbidity who may benefit from earlier or more aggressive intervention.